Composite membranes of the type utilized in one embodiment of the present invention have been previously described in U.S. Pat. No. 4,618,533 to Steuck. Some of the ion-binding ligands of the types disclosed herein are also known. For example, U.S. Pat. No. 4,952,321 to Bradshaw et al. discloses amine-containing hydrocarbons attached to a solid inorganic support such as silica or silica gel wherein the ligand is bound to the solid inorganic support through a hydrocarbon spacer containing a S trialkoxysilane group. U.S. Pat. Nos. 5,071,819 and 5,084,430 to Tarbet et al. disclose sulfur and nitrogen-containing hydrocarbons as ion-binding ligands. U.S. Pat. Nos. 4,959,153 and 5,039,419 to Bradshaw et al. disclose sulfur-containing hydrocarbon ligands. U.S. Pat. Nos. 4,943,375 and 5,179,213 to Bradshaw et al. disclose ion-binding crowns and cryptands as ligands. U.S. Pat. No. 5,182,251 to Bruening et al. discloses aminoalkylphosphonic acid-containing hydrocarbons ligands. U.S. Pat. No. 4,960,882 to Bradshaw discloses proton-ionizable macrocyclic ligands. U.S. Pat. No. 5,078,978 to Tarbet et al. discloses pyridine-containing hydrocarbon ligands. U.S. Pat. No. 5,244,856 to Bruening et al. discloses polytetraalkylammonium and polytrialkylamine-containing hydrocarbon ligands. U.S. Pat. No. 5,173,470 to Bruening et al. discloses thiol and/or thioether-aralkyl nitrogen-containing hydrocarbon ligands. U.S. Pat. No. 5,190,661 to Bruening et al. discloses sulfur-containing hydrocarbon ligands also containing electron withdrawing groups. Copending application Ser. No. 08/058,437 filed May 7, 1993, discloses oxygen donor macrocycles, for example, ligands containing macrocyclic polyether cryptands, calixarenes, and spherands, multiarmed ethers and mixtures of these. All of these previous reports have involved binding of the ligands to solid inorganic supports via a silane-containing spacer grouping. However, researchers have not previously reported incorporating complex, strongly interacting and highly selective ion-binding ligands into membranes which would be highly desirable because of the high surface-to-area ratios, convenient physical formats, ease of production, ease of use, and inexpensive cost of such membranes. The present invention successfully accomplishes this feat.